Coil form and carrier strip

ABSTRACT

A molded polymeric carrier strip having a plurality of coil forms integrally formed therewith in a fashion to permit automated terminal wire and coil attachment thereto, the coil forms being readily detachable from the carrier strip.

United States Patent Johnson et al.

[ 1 May 30, 1972 COIL FORM AND CARRIER STRIP Inventors: Richard A. Johnson, Mcl-lenry; Charles E. Jensen; John 0. Renskers, both of Crystal Lake, all of 111.

Assignee: Coilcraft, Inc., Cary, 11].

Filed: Jan. 27, 1970 Appl. No.: 6,157

US. Cl. ..206/56 AB, 29/203 D, 174/52,

. 206/D1G. 8, 206/65 F Int. Cl. ..B65d 73/02, 865d 85/62 Field 01 Search ..206/56 A, 56 AB, 65 F, DIG. 8;

References Cited UNITED STATES PATENTS 3/1969 Bus1er....

2/1968 Renskers ..336/65 9/1969 Boehmke ..206/65 F 1/1964 Rutkovsky et a1. 198/177 Primary ExaminerWi11iam T. Dixson, Jr. Att0rneyGradolph, Love, Rogers & Van Sciver ABSTRACT A molded polymeric carrier strip having a plurality of coil forms integrally formed therewith in a fashion to permit automated terminal wire and coil attachment thereto, the coil forms being readily detachable from the carrier strip.

5 Claims, 8 Drawing figures COIL FORM AND CARRIER STRIP BACKGROUND OF THE INVENTION This invention as described is directed basically to the mounting of small coils for insertion into electronic circuits, although it will be appreciated that the teachings here are ap plicable to the mounting of a variety of electronic circuit components for such purpose. The coils under consideration are employed notably in the television industry for peaking coils, radiofrequency chokes, fixed inductors, reactances, chokes, etc.', of limited power handling capacity all of which are of minimal size and are formed of a wire too small to be self-supporting. A representative coil might be of 42 gauge wire universally wound to have an external diameter of about three-tenths of an inch.

In U.S. Pat. No. 3,368,276 issued Feb. 13, 1968, to John O. Renskers et al., there is shown a mounted coil representing the state of the art upon which this invention is to improve. A small square or rectangular piece of vulcanized paper has relatively stiff terminal wires secured along opposite edges to extend a short distance beyond the paper at one end and a greater distance beyond at the other. The coil is glued to the face of the paper between the terminal wires and the leads of the coil are secured to the short ends of the terminal wires. Thereafter, in most cases, the coil thus mounted is encapsulated by a dipping process.

Although the mounting just described is exceedingly simple and inexpensive in its parts, it demands a number of manual operations or relatively slow machine operations which add to the cost of the completed mounted coil. Also, there are certain structural disadvantages to the mount described. Since the terminal wires of the patent occupy both sides of the paper panel, the panel must be large enough to contain the coil between and spaced from the terminal wires. The paper panels are processed in connected strips and the individually mounted coils broken off these strips following their completion. An edge of the paper panel is thus exposed on the line of breakage through which moisture may enter in unfavorable environments.

SUMMARY OF THE INVENTION The present invention is directed to a molded carrier strip supporting a number of integral coil forms or substrates whereby the forms are supported for optimal automation of circuit element mounting procedures. It, likewise, avoids the defects specified above. Other objects and advantages of this invention will appear in the course of the description of the specific embodiment thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a rear elevation of a molding incorporating this invention with terminal wires attached and with the right end of another like molding adjacent the left end thereof;

FIG. 2 is a side elevation of the left end of the molding of FIG. 1;

FIG. 3 is a top plan view, partially in section, of the molding of FIG. 1 taken along the line 3-3 of FIG. 1 looking in the direction of the arrows;

FIG. 4 is an enlarged rear elevation of a substrate detached from the carrier strip with a coil and terminal wires attached;

FIG. 5 is a top plan view of the form of FIG. 4;

FIG. 6 is a section taken along the line 6-6 of FIG. 4 looking in the direction of the arrows;

FIG. 7 is a section along the line 7-'7 of FIG. 4 looking in the direction of the arrows; and

FIG. 8 is a section along the line 8-8 of FIG. 1 across the adjacent strip ends looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT The combined substrate and carrier strip 10 of this invention is a molded product formed of thermoplastic material, nylon being particularly suitable, although other polymers may be readily employed.

The coil form or substrate 12 is a generally rectangular member secured to the carrier strip 14 by two legs 16 extending from what will be called here the upper comers 18 although, when the circuit element is mounted, assembly completed and the mounted element detached, these will undoubtedly be commonly called the lower corners. In the illustrated embodiment, a stud 20 having a dimple 21 in its outer end extends from the center of the front face 22 of the substrate.

The sides or vertical edges of the substrate are each equipped with alternating projections particularly illustrated in FIGS. 6 and 7 by which terminal wires 24 are secured thereto. As illustrated, there are three rearwardly opening hook projections 26 having a throat 23 dimension to receive accurately a relatively heavy and stiff terminal wire 24, and an outwardly flared entry 25 thereinto. The hook projections 26 are situated at upper and lower comers and in the center of the vertical edges with the lower projections extending beyond the bottom edge of the form as at 27. It will be appreciated that these lower extensions lack an inside wall. The throats of the hooks thus provide a single, discontinuous groove for each of the terminal wires.

Between the hook projections 26 there are lug projections 28 which extend out from the back side 30 of the substrate to partially block entrance to the throats of the hook projections 26. Since the plastic material of which the substrates are made has substantial flexibility, it will be noted that a terminal wire 24 may be laid into the gap between the lug ends 28 and the free, flared ends 32 of the hook projections (as projected vertically, one on the other) and bumped into the throats of the hooks by forcing the hooks slightly open to provide passage past the lug projections. The terminal wires will then be held securely within the resiliently returning hook ends by the lug projections 28.

The hook projections 26 at the top and bottom corners of the substrate project beyond the general top and bottom edges 34 and 36 respectively of the substrate. The projection beyond the edge 34 provides a spacing of the general body of the mounted circuit element above a circuit board, when the element is attached thereto, for ventilation purposes, etc.

The bottom edge 36 of the substrate has a central boss 38 extending therefrom equally as the corner hook projections 26. This boss 38 is T-shaped in end elevation as will be particularly noted in FIG. 5. The stem 40 of the T is coextensive in depth with the body of the substrate, and the cross arm 42 of the T is a thin extension of the front face of the substrate beveled upwardly as at 44.

The substrate desirably will have all possible edges and corners rounded to ensure good encapsulant coverage.

The carrier strip 14 is a rectangular body molded integrally with the coil forms or substrates 12 and is of a length to support as many of the coil forms as may be desired. In a typical embodiment, there may be 10 or 12 substrates per carrier strip. The substrates are connected to the carrier strip by legs 16 as stated before.

The legs 16 not only support the substrates but also act as sprues for the substrate cavities. Also, the forms must be capable of separation from the legs with minimum effort and with minimum gate area. Accordingly, the legs 16 taper from the greater thickness of the carrier strip to about half of the lesser thickness of the body of the substrate and are offset outwardly on the substrates so as to intercept the substrate cavities at the outer comers of the upper hook projections with a very small area gate 45.

As stated, the carrier strip is thick in comparison with the substrate bodies. Since the carrier strip is to constitute a header for the several substrate cavities, such thickness is desirable, and it likewise contributes to the strength and ease of manipulation of the entire assembly. It will be noted that the front faces of the substrates lie slightly behind the like face (hereafter front) 42 of the carrier strip. The carrier strip has grooves 44 extending transversely across the back side 45 thereof in alignment with the terminal wire containments of the hook and lug projections 26 and 28 to receive terminal strip opposite the substrates. The hook consists of a bight 50 spaced above the top edge of the carrier strip by a shank 52 a sufficient distance to accommodate the maximum leg length of terminal wire to be attached to the substrate without interference from the hook. It will be appreciated that the hook is in the same plane as the carrier strip. The width of the shank is such as to be contained between adjacent grooves 44, again to accommodate the terminal wire projections. The hook will occupy the exact center of the carrier strip.

Finally, the carrier strip contains provision at its ends for linking two or more strips together in a continuous strand. This provision is particularly illustrated in the adjacent strip ends of FIG. 1 and the section thereof of FIG. 8. The left end 56 of the illustrated strip incorporates an integral tongue 58 of reduced width extending centrally therefrom. The tongue 58 is about half the thickness of the strip with an offset therein including a root portion 60 coplanar with the front face of the strip, the offset 62, and a tip 64 having a rear face coplanar with the rear face of the strip. The illustrated, fragmentary, right hand strip end 66 has an arrangement complimentary to the tongue which consists of a through aperture 68 to receive the offset 62 of the tongue, a transverse outer rib 70 half the thickness of the strip having its rear face coplanar with the rear face of the strip to be accommodated within the slot 72 underlying the root 60 of the tongue, and an undercut 74 adjacent the inner end of the aperture to accommodate the tip 64 of the tongue. This arrangement has particular utility in that, referring to FIG. 8, the left hand strip may be situated flat on a table and the right hand strip connected to it by inserting the tip of the tongue vertically downward into the through aperture 68 and letting the right hand strip fall falt to the right upon the table, permitting exceedingly rapid connection.

The advantages of this structure are many. In the manufacture of mounted coils, for instance, the strips may be quickly and easily interconnected for continuous, automatic assembly operation. Both the insertion of the terminal wires and the placement of the coils or other circuit elements can be achieved by machine movements normal to the plane of the face of the substrates. The substrates are spaced along the carrier strip so that the spacing of the terminal wires is uniform both as between the wires of a single substrate and the adjacent wires of adjacent substrates. The coupling arrangement of the strips will maintain this uniformity of spacing across the couplings. No deformation of the terminal wires is involved. Thus, a single, simple, bumping tool can be employed for wire insertion without any irregularity in spacing.

The spacing of the substrates from the carrier strip permits ample lengths of terminal wire up to maximum requirements, which are well shielded and protected by the grooves in the carrier strip.

The inverted arrangement of the substrates on the carrier strip is likewise worthy of note. It is the short ends of the terminal wires to which the coil leads are secured and which are involved in soldering, bending, and encapsulation. These ends lie on the free outer edges of the substrates for convenience of manipulation.

The very fact that the substrates are separate from each other and attached only to the carrier strip is of further advantage. In prior practice where segments of a paper web constituted the substrate itself, it was the practice to handle the coils in connected strips for final operations including a terminal encapsulation. After the encapsulation the strips were broken apart leaving exposed an edge of the paper on each side, contributing possibly to moisture absorption. Also, the strips would not always break exactly on the desired line separation but rather along the line of tenninal wire attachment. These difficulties are wholely obviated here in that the encapsulation is virtually entire, the only exposure of the nylon form being at the exceedingly small gates. Also, the substrates being separate, the possibility of breaking along an undesired line does not present itself.

The projection 38 defines a pair of pockets on either side thereof into which the short terminal wire ends with the coil leads, for instance, attached thereto may be bent so as to keep the confines of the mounted coil at its upper end at least within the pictured bounds of the substrate. The stem 40 of the projection isolates the terminal wire ends from each other and the thin web constituting the cross arm 42 of the T provides an insulating front cover to prevent possible contact of the coil proper with the ends of the terminal wire. Thus a coil may be mounted to the front face of the substrate which has a diameter equal to or greater than a transverse dimension of the substrate and still be safely displaced in plane away from any parts of the temiinal wires.

Certain operations such as the encapsulation step are better handled by a manipulation of the carrier strip individually rather than in connected lengths. Just as the strips are easily connected, they may be as easily disconnected. The hook 48 permits a dipping of the several substrates associated with the carrier strip into an encapsulant and the convenient and compact storage of the several separate strips on a wire, for instance, in transverse parallel relation for drying and curing. The very small andinsubstantial connection of the substrate to the legs 18 permits an easy breaking off of the mounted elements from the carrier strip. Once the elements have been mounted in the described fashion and broken off the carrier strip, the carrier strip may be returned to the molding operation and reprocessed for the production of further combined substrates and carrier strips.

The stud 20 likewise facilitates assembly procedures. It provides a centering post for the exact placement of the coils, and after the coils are emplaced, they may be secured to the substrate by mushrooming over the tip of the stud by the application of heat or an ultrasonic transducer.

Certain variations are specifically contemplated. The stud 20 may be shorter than shown to serve a centering function only, may be lacking, or a hole through the substrate may occupy its place, as where a tunable coil may be desired. The hook 48 may be replaced by other supporting means, or may be lacking altogether with the indexing holes 46 employed for supporting purposes.

Other structural variations will undoubtedly suggest themselves to meet particular design characteristics or assembly procedures.

We claim:

1. A combined, integrally molded carrier strip and electronic circuit element substrate assembly comprising a strip having a long axis and a plurality of spaced, generally planar substrates, having terminal wire holding means thereon extending transversely of the axis of said strip, projecting independently laterally from and substantially spaced from a longitudinal edge of said strip, integral with said strip.

2. The combination as set forth in claim 1 wherein each substrate has two terminal wire holding means and said substrates are spaced apart on said strip a distance such that the spacing of adjacent means of adjacent substrates is equal to the spacing of the means of one substrate.

3. The combination as set forth in claim 1 including additionally transverse grooves in said'carrier strip aligned with said wire holding means.

4. The combination as set forth in claim 1 including means at the ends of said strip for detachably connecting like strips to said strip in end to end relationship, and central means for suspending said strip on that edge thereof remote from said substrates in side by side relation to like strips on a single, linear support.

5. The combination as set forth in claim 4 wherein said central means is a hook extending from said remote edge and oriented longitudinally with said strip.

F k k 

1. A combined, integrally molded carrier strip and electronic circuit element substrate assembly comprising a strip having a long axis and a plurality of spaced, generally planar substrates, having terminal wire holding means thereon extending transversely of the axis of said strip, projecting independently laterally from and substantially spaced from a longitudinal edge of said strip, integral with said strip.
 2. The combination as set forth in claim 1 wherein each substrate has two terminal wire holding means and said substrates are spaced apart on said strip a distance such that the spacing of adjacent means of adjacent substrates is equal to the spacing of the means of one substrate.
 3. The combination as set forth in claim 1 including additionally transverse grooves in said carrier strip aligned with said wire holding means.
 4. The combination as set forth in claim 1 including means at the ends of said strip for detachably connecting like strips to said strip in end to end relationship, and central means for suspending said strip on that edge thereof remote from said substrates in side by side relation to like strips on a single, linear support.
 5. The combination as set forth in claim 4 wherein said central means is a hook extending from said remote edge and oriented longitudinally with said strip. 